On Jan 20, 11:29*am, JIMMIE wrote:


On a lot of AM auto radios the SN ratio really stinks and an external
preamp especially one with some preselection can really help. As
previously stated on radios with adequate sigal to noise ratio adding
a preamp just makes things worse.

Jimmie

I wouldn't say that. Most all the auto AM radios I've had were
quite good. Always plenty of sensitivity as long as the antenna
was functioning correctly.
The current car I'm driving "Corolla" uses a small helically wound
antenna, which is at the rear of the roof. It's pretty short overall,
and I still have plenty of sensitivity. The daytime is the best time
to check that, and I've never had any trouble receiving out of
town stations. And if I tune to an open frequency, I hear background
atmospheric noise, so any increase in sensitivity is pretty much
useless. I've had older Delco radios in cars and the AM was
excellent on those.
If the OP can hear background noise when tuned to an empty
frequency, and not have it sound "dead", adding more pre-amp
is unlikely to help.
I think the main culprit in this case is propagation, and the
pattern of the array, and unfortunately, I think he's basically
out of luck. Normally you would probably be able to hear the
ground wave out to at least 200-300 miles in the daytime,
but that assumes a fairly stout signal. If the pattern is away
from that direction, even the ground wave possibilities start
to look kind of bleak.
If an auto AM radio does not have enough sensitivity, it usually
means there is something wrong with it, or the antenna.
Most as they come from the factory have more than enough.